Image processing apparatus, image processing method, and computer-readable storage medium

1. An image processing apparatus configured to determine a correction parameter used for line width correction from among a plurality of candidate parameters, the image processing apparatus comprising: an output unit configured to output a line width chart obtained by printing a plurality of straight lines subjected to line width correction using the plurality of candidate parameters as line width patches; a reading unit configured to read the line width chart output by the output unit to acquire respective images of the line width patches; an acquisition unit configured to acquire pixel values of pixels in the images of the line width patches acquired by the reading unit; a generation unit configured to generate, for each of the line width patches, a line width profile representing a distribution of the pixel values acquired by the acquisition unit; a storing unit configured to store a reference profile representing a distribution corresponding to a predetermined line width; and a determination unit configured to determine the correction parameter from among the plurality of candidate parameters based on a comparison between the distribution represented by each line width profile generated by the generation unit and the distribution represented by the reference profile stored in the storing unit.

2. The image processing apparatus according to claim 1 , wherein the generation unit generates the line width profile using index values respectively obtained for a plurality of pixel columns parallel to an extension direction of the straight lines printed as the line width patches, based on the pixel values acquired by the acquisition unit; and wherein the determination unit compares the index values respectively obtained for the plurality of pixel columns included in the line width profiles with a plurality of index values included in the reference profile, to determine the correction parameter.

3. The image processing apparatus according to claim 2 , wherein the generation unit averages the pixel values of the plurality of pixels included in the pixel columns and acquired by the acquisition unit, to respectively obtain average pixel values for the pixel columns, and sets the average pixel values as the index values included in the line width profile.

4. The image processing apparatus according to claim 2 , wherein the determination unit calculates a cumulative difference between the index values respectively obtained for the plurality of pixel columns included in the line width profile and the plurality of index values included in the reference profile, and determines the candidate parameter corresponding to the line width profile having the smallest cumulative difference as the correction parameter.

5. The image processing apparatus according to claim 1 , wherein the storing unit stores the line width profile generated by the generation unit as the reference profile used for the comparison by the determination unit according to a user's instruction.

6. The image processing apparatus according to claim 1 , wherein the storing unit stores the reference profile for each of a plurality of read characteristics, and wherein the determination unit selects the reference profile corresponding to read characteristics of the reading unit acquiring images of the straight lines from the plurality of reference profiles, and compares the selected reference profile with the line width profile generated by the generation unit, to determine the correction parameter.

7. The image processing apparatus according to claim 1 , wherein the storing unit stores the reference profile of each of a plurality of types of paper on which an image to be subjected to the line width correction is printed, and wherein the determination unit selects the reference profile corresponding to a type of paper on which an image to be subjected to the line width correction is printed, from among the plurality of reference profiles, and compares the selected reference profile with the line width profile generated by the generation unit, to determine the correction parameter.

8. The image processing apparatus according to claim 1 , further comprising a display unit configured to display a message to a user, wherein the generation unit acquires a skew amount of the line width chart read by the reading unit, and displays a reread message of the line width chart by the reading unit on the display unit when the skew amount is equal to or greater than a predetermined threshold value.

9. The image processing apparatus according to claim 1 , wherein the acquisition unit acquires luminance values of the pixels as the pixel values.

10. The image processing apparatus according to claim 1 , wherein the correction parameter includes adjustment items of color, direction, line width, and density.

11. The image processing apparatus according to claim 1 , wherein the correction parameter is different depending on an attribute of an image included in the image to be subjected to the line width correction.

12. The image processing apparatus according to claim 1 , wherein the output unit, the reading unit, the acquisition unit, the generation unit, the storing unit, and the determination unit are configured to function when gradation correction processing is performed.

13. An image processing method for determining a correction parameter used for line width correction from among a plurality of candidate parameters, the method comprising: outputting a line width chart obtained by printing a plurality of straight lines subjected to line width correction using the plurality of candidate parameters as line width patches; reading the output line width chart to acquire respective images of the line width patches; acquiring pixel values of pixels in the acquired images of the line width patches; generating, for each of the line width patches, a line width profile representing a distribution of the acquired pixel values; determining the correction parameter from among the plurality of candidate parameters based on a comparison between the generated line width profile and a reference profile representing a distribution corresponding to a predetermined line width.

14. A non-transitory computer-readable storage medium storing a program which causes a computer to perform the image processing method according to claim 13 .

15. An image processing apparatus configured to correct an image using a correction parameter to print a line of the image in a predetermined line width, the image processing apparatus comprising: a printing unit configured to print a line width patch; a reading unit configured to read an image of the printed line width patch; a generation unit configured to acquire pixel values of pixels in the read image of the line width patch and to generate a line width profile representing a distribution of the acquired pixel values; a storing unit configured to store a reference profile representing a distribution of pixel values corresponding to the predetermined line width; a determination unit configured to determine the correction parameter based on a comparison between the distribution represented by the line width profile acquired by the generation unit and the distribution represented by the reference profile stored in the storing unit; and a correction unit configured to correct a line width of an image using the correction parameter determined by the determination unit.